Development is charactarized by increasing flexibility in thought and action, enabeling the generalization of rules from item-specific instances to abstract classes of rules that support flexible behavior and can be generalized to novel situations. We capitalized on an established paradigm that has been effective in charactarizing this skill in adults in behavioral and fMRI experiments, and also in patients with frontal damage. This work has shown that increasing complexity in rule-guided action recruites the frontal cortex along a rostro- caudal axis. We hypothesize here that the functional development of the frontal cortex, from middle childhood to adulthood, and associated behavioral performance will follow the same pattern. Specifically, we predict that mature behavior in simple rule tasks will be evident earlier in development than more complex tasks and that this will be associated with functional effiency at the level of the frontal cortex in caudal prior to rostral regions. Using th extant literature, we predict that this functional development is a reflection of increases in the stability of cortical coding of rule-relevant representations. We test this hypothesis using multi-voxel pattern classification algorithms designed to decode the stability of rule-relevant representations across development. Moreover, we test the prediction that representational stability is dependent on experience. Portions of the frontal cortex have an especially protracted developmental course and have been shown to be susceptible to both positive and negative environmental experiences. Rather than use age as a proxy for experience, we turn to socioeconomic status (SES), which has been shown to be a predictor of cognitive control development. Availability of items, interactions, and experiences in high relative to low SES families may prove relevant for experience-based changes in representational stability at the level of the frontal cortex. Moreover, variability among experiences is necessarily more relevant for the development of abstract rather than concrete rule representations, indicating that the impact of SES differences may be evident specific to the development of abstract rule structures. We will examine the specific contribution of SES, as a proxy for enriching experiences, to the development of rule-guided action in both behavioral and neuroimaging experiments. RELEVANCE Item-specific concreteness and perseveration are ubiquitous in developmental disorders including Autism, ADHD, and OCD. We propose to characterize development of rule use at varying levels of abstraction, allowing for novel specificity in understanding the deveopmental course of these skills. Uncovering a specific relationship with experience-based factors (SES) in this development has the added potential of defining variables that confer risk specific to cognitive flexibility and will inform social and educational policy moving forward. PUBLIC HEALTH RELEVANCE: We focus this work on the development of cognitive control and rule-guided behaviour during the transition from childhood to adolescence and adulthood. This is a period marked by extensive change in the child's environment, including changes in peer relations and increased independence and academic demand. Our aim is to expose the developmental interactions among components of rule-guided behaviour, their functional neural substrates, and the nature and stability of rule-relevant representations coded by the frontal cortex across this developmental period.